James Hanley

For Reference, I only work in audio so my needs are strictly AC and minimal.  I have 2 Tektronix scopes, a 2213A analog and a 2430 Digital. 

The digital 2430 had been working but suddenly Focus went blurry.  I can't get a line, only a smudge.  The smudge reacts to signal as from the Calibration terminal but is useless as a smudge. Neither Focus nor Astigmatism controls are able to bring the display back into line.

The analog 2213A is obviously old but new to me and while seller says "works great !", it doesn't.  The screen remains blank other than general backlighting until "Beam Finder" button is engaged.  Then a smudged dot appears that is reactive to signal but again, smudging is useless.  Controls like position and focus seem to have some effect but never does any horizontal deflection appear, IOW always a dot that will extend vertically but never a horizontal line.

I'm  moderately aware capacitors are common problems but before I tear into either my question is simple -  Which one is easier/cheaper to fix?

Greetings and please accept my apologies for such a fundamental question but I am an old analog guy who never wants to measure DC with my Model 2430.  I am long retired and just like to build, modify and repair old tube/valve gear.  For example I want to be able to view audio frequency signals on output transformer primaries that may be riding on 500vdc.

I bought this Tektronix 2430 used after my even more ancient analog scope died after decades of service.  Do I need a specific probe or can I set this model to default to measuring AC signals only.  I see a trigger mode set that will allow me to set to AC as well as a "LF Reject" but neither allows me to view AC signal riding on DC.  The trace just leaves the screen.

Obviously I could jury rig a 600v capacitor in series with the probe but that seems Rube Goldberg clunky.   What do I need or what am I doing wrong?